* lisp.h (last_glyphless_glyph_frame, last_glyphless_glyph_face_id)

* lisp.h (last_glyphless_glyph_frame, last_glyphless_glyph_face_id)
(last_glyphless_glyph_merged_face_id): Remove declarations.
* dispextern.h (merge_glyphless_glyph_face): Add prototype.
* xdisp.c (last_glyphless_glyph_frame, last_glyphless_glyph_face_id)
(last_glyphless_glyph_merged_face_id): Now static.
(merge_escape_glyph_face): New function, refactored from...
(get_next_display_element): ...here.
(merge_glyphless_glyph_face): New function, refactored from...
(produce_glyphless_glyph): ...here...
* term.c (produce_glyphless_glyph): ...and here.